Not Applicable.
Not Applicable.
The present invention relates generally to the field of acoustic agglomeration, and more particularly, but not by way of limitation, to a modulated acoustic agglomeration system and method for removing constituents in a fluid stream.
Fluid streams comprising small constituents are produced by many chemical and combustion processes, such as, but not limited to, particulates in the exhaust gas stream of coal fired power plants. Such particulate matter is undesirable and should be removed before the gas stream is passed to equipment or processes and released into the atmosphere. It is particularly challenging to remove such particulate matter from high temperature gas streams in large volumes exhausted from boilers of such power generating facilities.
Particles which are over ten microns in diameter are frequently removed from gas streams by conventional porous filters, such as bag houses and the like, but smaller particles are much more difficult to remove because the porosity of the filter must be so small to capture these fine particles that it creates a substantial pressure drop across the filter. The pressure drop is problematic, consumes energy resources and may inhibit the combustion process. Therefore, porous filters cannot remove small particles from gas streams efficiently.
From time to time, particulates in a gas stream collide with one another and may naturally agglomerate with other such particles on impact to form larger agglomerate particles. This agglomeration is beneficial because the agglomerated particles are larger and thus susceptible to filtration from the porous filters. However, such incidences of natural agglomeration are limited. Increasing the incidence of collisions and agglomeration results in a reduced emission of such particulates into the atmosphere. For this reason, many methods of agglomerating these particles have been employed. The number of collisions may be increased by confining the gas stream in a tube, flue, or duct and subjecting the particles to a sonic or acoustic field. This process is referred to as acoustic agglomeration and has been employed to agglomerate small particles into larger agglomerates.
However, methods of acoustic agglomeration are frequently inefficient in that the power consumption required by such devices negates the benefits achieved by only marginal reduction in the particulates exhausted into the atmosphere. Methods of acoustically agglomerating particulates employing a sound source emitting a fixed or constant frequency or employing a pulse combustor producing a saw-tooth wave have been employed.
Such systems, however, suffer from deficiencies including lacking sufficient control of the particulate agglomeration, failing to agglomerate particulates of a small size, and inefficiency in agglomeration and power consumption when compared to the actual reduction in particulate emission. Additionally, small particulates, such as those below ten microns, continue to be difficult to successfully agglomerate into particulates of sufficient size for treatment by filter processes by generally accepted methods of employing acoustic agglomeration.
Thus, a need exists for an improved system and method for acoustically agglomerating constituents in a fluid stream. Furthermore, a need exists for a more efficient system and method for acoustically agglomerating particulates in the fluid stream capable of achieving consistent and controlled constituent agglomeration. It is to such an acoustic agglomeration system and method that the present invention is directed.
In one aspect, the present invention is directed to a method for agglomerating constituents in a fluid. The method broadly includes providing a fluid with a constituent and applying an acoustic field to the fluid. The method further includes modulating the acoustic field to cause the constituent to agglomerate.
In one aspect of the present invention, the acoustic field is amplitude modulable, in another aspect the acoustic field is frequency modulable, while yet in other aspects the acoustic field is both frequency and amplitude modulable.
One advantage of the present invention is that frequency, amplitude and/or a combination of frequency and amplitude modulation of the acoustic field applied to a fluid containing constituents significantly improves agglomeration of the constituents. In one aspect, the frequency of the acoustic field is modulable in a range of up to 1 GHz and the amplitude of the acoustic field is modulable in a range of up to 200 dB referenced to 20 micro-Pascals.
In other aspects, the frequency of the acoustic field is modulable in a range of up to 20 kHz and the amplitude of the acoustic field is modulable in a range of up to 200 dB referenced to 20 micro-Pascals. While in other aspects, the frequency of the acoustic field is modulable in a range of from about 50 Hz to about 15 kHz and the amplitude of the acoustic field is modulable in a range of from about 130 dB to about 175 dB referenced to 20 micro-Pascals.
In one aspect, the fluid is a liquid. In other aspects, the fluid is defined as a gas or may be a combustion exhaust gas, while in yet other aspects the constituent of the combustion gas is fly ash.
In one aspect, the method includes applying a plurality of acoustic fields to the fluid. In another aspect, each of the plurality of acoustic fields are provided with the same frequency, amplitude and/or combination of frequency and amplitude modulation. While in other aspects, the plurality of acoustic fields are provided at a different frequency, amplitude and/or combination of frequency and amplitude modulation. While still in other aspects, some of the plurality of acoustic fields are provided at the same frequency, amplitude and/or combination of frequency and amplitude modulation and others of the plurality of acoustic fields are provided at a different frequency, amplitude and/or combination of frequency and amplitude modulation.
In one aspect the acoustic field has an initial frequency and the acoustic field is frequency modulated relative to the initial frequency to cause the constituent to agglomerate. In another aspect, the acoustic field is modulated to a first frequency substantially less than the initial frequency, while in other aspects the acoustic field is modulated to a first frequency substantially greater than the initial frequency. In one aspect, the acoustic field may be modulated to a second frequency substantially greater than the first frequency, while in other aspects, the acoustic field is modulated to a second frequency substantially greater than the initial frequency. In yet other aspects, the acoustic field may be modulated to a second frequency substantially less than the first frequency, while in other aspects the acoustic field is modulated to a second frequency substantially less than the initial frequency.
In one aspect, a method for agglomerating constituents in a fluid stream is provided that includes providing the fluid stream containing a constituent into a fluid passageway adapted to communicate the fluid stream. The method provides for applying an acoustic field to the fluid stream in the fluid passageway and modulating the acoustic field in the fluid passageway to cause the constituent to agglomerate in the fluid stream.
In yet another aspect, an acoustic agglomerator for agglomerating constituents in a fluid is provided. The acoustic agglomerator includes an acoustic plate, a shaft and a mechanical oscillator. The acoustic plate is configured for acoustic generation. The shaft has a first end and a second end, the first end of the shaft connected to the acoustic plate. The mechanical oscillator is connected to the second end of the shaft for imparting an oscillation thereon the shaft and the acoustic plate connected thereto for generating a modulated acoustic field.
In one aspect, an acoustic agglomerator for agglomerating constituents in a fluid stream is provided. The acoustic agglomerator includes a duct, a manifold system and at least a first sound source. The duct has a sidewall defining a fluid passageway, the duct is adapted to receive the fluid stream having the constituents. The manifold system is coupled to the duct such that the manifold system communicates with the fluid passageway. The at least a first sound source is coupled to the manifold system and is operable to generate a modulated acoustic field within the fluid passageway of the duct.
In yet another aspect, an acoustic agglomerator for removing particulates from a fluid stream is provided. The acoustic agglomerator includes a duct, an acoustic generator and a particle collection device. The duct has a sidewall defining a passageway, the duct is operable to receive the fluid stream having particulates. The acoustic generator is adapted to generate a modulated acoustic field in the fluid passageway of the duct. The particle collection device communicates with the duct to receive the fluid stream therefrom the duct. The particle collection device adapted to remove at least a portion of the particulate from the fluid stream.
In one aspect, the acoustic agglomerator further includes a plurality of acoustic generators each capable of generating a modulated acoustic field in the fluid passageway of the duct.
Other objects, features, and advantages of the present invention will be apparent to those skilled in the art from the following detailed description when read in conjunction with the accompanying drawings and appended claims.